This invention relates generally to improvement in cargo carriers for external mounting on aircraft and is particularly directed to a joint for shaped tank constructions for nested packaging.
Presently existing aircraft jettisonable fuel tanks are manufactured from sections of cylindrical or elliptical sections secured together by some type of tension device. Typical tension devices include a split clamp circumscribing flanges on the distal ends of the sections joined as in U.S. Pat. No. 3,469,730 to Neff, et al, or some type of longitudinal tension device running through the tank, as disclosed in U.S. Pat. No. 2,653,541 to Kanode, et al, all of which lack a positive mechanical structural joint. The lack of a positive structural joint may permit the sections to separate or leak in certain flight maneuvers due to resultant bending stresses at the joints. As a result, flight restrictions are imposed restricting aircraft performance in terms of maneuvering load factors, especially when fully fueled. Further restrictions are also present which limit tank jettisoning to a very narrow flight envelope.
The lack of a positive mechanical joint at the tank sections also creates a serious lightning strike problem, since the prior joint designs inherently do not assure a high quality electrical bond between tank sections. Since lightning strikes are primarily to a nose cone portion of the tank, and secondarily to the tank aft cone, any electrical charge will travel to the airframe attach section. Since this section is at airframe potential, unless a high quality bond exists between sections, arcing will occur across the joints with possible catastrophic detonation of a fuel/air mixture in the tank.
The tank section joint concept, to a large degree, also defines the fluid sealing problem. Leakage problems have been particularly prevalent where longitudinal joints are used in combination with peripheral joints due to intersecting seals.
In summary, contemporary aircraft external fuel tanks have problems of excessive shipping space, slow assembly, seal leakage, lack of positive mechanical structural joints, and lack of lightning resistance compatibility.